JP2001009410A - Method for solubilization treatment of organic waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solubilize an organic waste to a high degree at a low cost. SOLUTION: An organic waste 1 and water are supplied to a solubilization tank 4 as a sealing chamber and mixed to obtain a slurry 3. If the carbonate ion concentration of the slurry 3 is >=1000 ppm, the slurry is heated to 120 to 350 deg.C in the solubilization tank to slubilize the organic waste 1. If the concentration of carbonates or bicarbonates in the scurry 3 is less than 1000 ppm, carbonates or bicarbonates having Na, K, Ca, Mg, Ba or NH4 as cations or a mixture of these are externally added to the slurry 3, or the slurry 3 is aerated with carbonic acid gas to increase the concentration of carbonate ion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to kitchen waste and human waste, excess sludge discharged from an aerobic or anaerobic water treatment facility such as a human waste treatment plant or a sewage treatment plant, or livestock waste. The present invention relates to a method for solubilizing an organic waste contained in digestion residue after digestion treatment of the organic waste alone or a mixture of organic waste such as livestock manure, straw, wood chips, and bark. .

[0002]

2. Description of the Related Art In digestion treatment in which methane gas is produced by the action of microorganisms using organic waste as a raw material, mainly,
Because it is intended for organic matter that dissolves in water, when processing a slurry containing solid matter of organic waste, it takes time for the solid matter in the slurry to dissolve, and the residence time in the digestion tank increases. From several weeks to one
A processing period of about a month was required.

[0003] Therefore, after solubilizing organic waste,
As a method for efficiently performing the digestion treatment, for example, an alkaline substance is added to organic sludge to adjust the pH to 7.3 to 9.2.
And a pretreatment is performed by maintaining the treatment temperature at 50 to 100 ° C. to enable a high-load digestion treatment (Japanese Patent Application Laid-Open No. 5-345200). Kitchen garbage is solubilized using enzymes, the cellulose fibers in the kitchen garbage slurry (mixture of kitchen garbage and water) are refined, then separated into three phases by the difference in specific gravity, and the phase rich in kitchen garbage is digested. A method in which digestion treatment is easily performed by treating (Japanese Patent Publication No. 60-9879) has been proposed.

[0004]

However, in the case of the former method disclosed in Japanese Unexamined Patent Publication No. 5-345200, a large amount of alkaline substance is required to adjust the pH of the alkaline treatment from 7.3 to 9.2. It is necessary to adjust the pH to around 9 in order to consume more and to solubilize the sludge more effectively. Therefore, when the solubilized treatment liquid is put into the digestion tank, it is necessary to reverse neutralize with acid. was there. In addition, the processing temperature is required to be 50 ° C. or higher, and when promoting more efficient solubilization, high-temperature processing of about 100 ° C. is required. However, since the heat treatment is not performed in a closed container, the processing pressure is as low as about atmospheric pressure. As a result, the solubilization rate of organic matter from the sludge was kept at a low level.

On the other hand, in the case of the latter method disclosed in Japanese Patent Publication No. 60-9879, the price of the enzyme to be used is extremely high, and it is not practical to add an enzyme at a concentration at which an effect is obtained. This cannot be adopted at all when considering implementation in a plant. Separating the specific gravity into three phases and digesting the phase containing a large amount of garbage can simplify the digestion process itself, but realizes this method in consideration of other wastewater and residue treatment. It is very difficult.

[0006] As described above, in the digestion treatment using organic waste as a raw material, in order to improve the digestion efficiency, the organic waste is solubilized so as to have a low molecular weight that is easily taken up by microorganisms. In this case, the conventional method has a problem that the level of solubilization of the organic waste is low and the processing cost is high.

Incidentally, a method of decomposing organic sludge in a supercritical state of water by heating in a closed vessel is disclosed in Japanese Patent Application Laid-Open No. 9-99-1991.
No. 276900, this method uses:
Since organic sludge is almost completely decomposed into carbon dioxide and water, it is not possible to convert organic waste into low-molecular-weight organic substances that can be easily taken up by microorganisms. , High temperature (more than 374 ° C) and high pressure (22
(MPa or more) requires a lot of cost to generate such conditions, which is not preferable from an economic viewpoint.

Accordingly, the present invention provides a method for solubilizing organic waste at a low cost by heating the organic waste in a closed vessel at high temperature and high pressure, and at a high level. It is an object of the present invention to provide a method for solubilizing an organic waste, which can carry out the process.

[0009]

According to the present invention, in order to solve the above-mentioned problems, an aqueous solution obtained by dispersing an organic waste having a carbonate ion concentration of 1000 ppm or more in an airtight container at 120 to 350 ° C. By heat treatment to
An organic waste solubilization method for solubilizing the organic waste is provided.

When the aqueous solution raw material contains carbonate ions at a concentration exceeding 1000 ppm, the organic waste is solubilized even at a low temperature of about 120 ° C., so that a high temperature and a high pressure for generating a supercritical state of water cannot be obtained. do not need.

[0011] When an aqueous solution of an organic waste having a carbonate ion concentration of 1000 ppm or less is used, a carbonate containing Na, K, Ca, Mg, Ba or NH ₄ as a cation is contained in the slurry. Alternatively, the same effect can be obtained by adding a bicarbonate or a mixture thereof, or by increasing the concentration of carbonate ions in the slurry to 1000 ppm or more by aerating a gas containing carbon dioxide gas.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the method for solubilizing organic waste according to the present invention. The solubilization tank is a sealed container for solubilizing organic waste 1 such as kitchen garbage. 4 and water 2 together with the organic waste 1 and
An example in which the slurry 3 is formed and the concentration of carbonate ions in the slurry 3 is 1000 ppm or more will be described. That is, in a state where the slurry 3 having a carbonate ion concentration of 1000 ppm or more is accommodated in the solubilization tank 4, the slurry 3 is heated at 120 to 350 ° C.
The organic waste 1 is solubilized by heat treatment, and then the solubilized material 5 as a treatment liquid
To the digestion tank 6 downstream, where the solubilizate 5
To generate methane gas 7. Reference numeral 8 denotes a digestion residue containing cellulose, lignin and the like discharged from the digestion tank.

In the above description, since carbonate ions promote the solubilization of solids, if the carbonate ions are contained in the slurry 3 in an amount of 1000 ppm or more, 120 ppm in the solubilization tank 4 which is closed. Under the subcritical condition of water of heating to 350 ° C., the organic waste 1 which is a solid can be solubilized. As a result, the organic matter in the solubilized substance 5 sent from the solubilization tank 4 to the digestion tank 6 can be a small molecule that can be easily taken up by microorganisms. Therefore, the methane gas 7 is generated in the digestion tank 6 with high efficiency. In addition, since a large amount of carbonate ions can be sent into the digestion tank 6, the digestion rate in the digestion tank 6 can be improved, and the digestion tank 6 can be downsized. . The methane gas 7 generated in the digestion tank 6 can be used as a fuel for power generation or the like, and the waste heat generated at that time can be used as a heat source for heating the solubilization treatment tank 4; By putting the generated CO ₂ into the solubilization tank 4, carbonate ions can be generated.

The treatment time required for solubilizing the organic waste 1 in the solubilization treatment tank 4 is 5 minutes or more, and the effect appears. After that, the effect does not decrease even if the time is long. It is practical to process within one day.

In the above embodiment, when there is no carbonate ion, the addition of sulfate, sulfite, nitrate, nitrite, or phosphate in the presence of any anion derived from each of these salts will result in: Since the solubilization phenomenon of the organic waste 1 cannot be confirmed, it can be said that the carbonate ion has an inherent action.

Next, FIG. 2 shows another embodiment of the present invention, in which the concentration of carbonate ions in a slurry 3 as an aqueous solution material obtained by dispersing an organic waste 1 is 1000 pp.
An example of application to the case of less than m will be described. That is, the slurry 3 in which the concentration of carbonate ions is less than 1000 ppm,
In a state in which it is accommodated in the solubilization tank 4 similar to that shown in FIG. 1, as the additive 9, carbonate containing Na, K, Ca, Mg, Ba, or NH ₄ as a cation is contained in the slurry 3. Salt or bicarbonate (bicarbonate), or a mixture thereof is added and heat treatment is performed at 120 to 350 ° C. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals.

As described above, when the concentration of carbonate ions in the slurry 3 is lower than 1000 ppm, a carbonate, a bicarbonate, or the like is added from the outside as an additive 9, and
By increasing the concentration of carbonate ions therein, the organic waste 1 can be efficiently solubilized as in the embodiment of FIG.

In the above, cations constituting carbonates and bicarbonates have the same effect as long as they are Na, K, Ca, Mg, Ba and NH _4. It is suitable. The amount of additive 9 is
The concentration of carbonate ion in the slurry 3 after the addition is 1000 pp
m or more is required.

Further, the above-mentioned carbonate or bicarbonate serves as a substrate for the digestion reaction and is converted into methane as a result of the biological reaction, so that the amount of methane gas 7 generated in the digestion tank 6 can be improved.

FIG. 3 shows still another embodiment of the present invention. Similar to the embodiment shown in FIG. 2, when the concentration of carbonate ions in the slurry 3 is less than 1000 ppm, FIG. Instead of adding carbonate, bicarbonate or the like to the slurry 3 as in the case of the second embodiment,
A gas 10 containing carbon dioxide gas is aerated in the slurry 3,
This is to increase the concentration of carbonate ions in the slurry 3.

In the case of the embodiment shown in FIG.
PH decreases, but the concentration of carbonate ion is 1000 to 5
Since the pH is about 4 in the range of 000 ppm, the slurry 3 can be heat-treated as in the above embodiment. Also, if the required amount of carbon dioxide gas is dissolved, the effect of solubilization itself does not change,
Because it may lower the pH of the slurry to 3 or less,
In such a case, a neutralization treatment may be performed with an alkali such as caustic soda.

In the case of the embodiment shown in FIG. 3, the gas 10 containing carbon dioxide gas for generating carbonate ions may be a boiler exhaust gas, a digester 6 exhaust gas, or a digester 6.
Because the combustion gas generated by burning the methane gas 7 obtained in the above can be used, the cost can be reduced with simple equipment and the amount of carbon dioxide gas released into the atmosphere can be reduced. Can be.

FIG. 4 shows still another embodiment of the present invention. The same solubilization tank 4 as shown in FIG.
Is provided downstream of the digestion tank 6 for supplying the slurry 3 of the organic waste 1 to perform the digestion treatment, and the digestion discharged from the digestion tank 6 while including the undecomposed organic waste 1 is included. The residue 11 is accommodated in the solubilization tank 4 as an aqueous solution material in which the organic waste 1 is dispersed, and when the concentration of carbonate ions in the digestion residue 11 is 1000 ppm or more, The concentration of carbonate ions in the medium is 1000pp
In the case of less than m, the same additive 9 as shown in FIG. 2 is added to the digestion residue 11 as shown by the two-dot chain line in FIG. 4, or as shown by the one-dot chain line in FIG. By performing the same aeration of the gas 10 containing carbon dioxide as shown in FIG. 3, the concentration of carbonate ions in the digestion residue 11 is 1000 pp.
m, the organic waste 1 in the digestion residue 11 is solubilized by heating to 120 to 350 ° C. in the solubilization tank 4. Is sent again to the digestion tank 6 to perform digestion processing. Reference numeral 13 denotes a residue containing cellulose, lignin, and the like that are not solubilized in the solubilization tank 4. In addition, the same portions as those shown in FIG. 1 are denoted by the same reference numerals.

According to the present embodiment, the undecomposed organic waste 1 in the digestion residue 11 discharged from the digestion tank 6 is recovered, so that the amount of methane gas 7 generated can be increased. The amount of the residue 13 to be discarded can be reduced.

It should be noted that the present invention is not limited to the above-described embodiment, and that the solubilization tank 4 may be pressurized by applying an external pressure when heating the solubilization tank 4. Of course, various changes can be made without departing from the spirit of the present invention.

[0027]

The results of experiments conducted by the present inventors will be described below.

(1) Example 1 Kitchen garbage in the presence of water was removed from the kitchen garbage under the conditions shown in Table 1.
The solubilization treatment was carried out by variously changing the concentration of the carbonate ion by setting the treatment temperature to 150 ° C. and the treatment time to 1 hour in wt%. The results were as shown in Table 2.

[Table 1] [Table 2] As is clear from Table 2, when carbonate ions are present at a high concentration of 1000 ppm, organic substances can be decomposed at a high rate of 78% or more as shown in Category 4. At this time, the sugar concentration ( g / l) is 1.818, COD concentration (g / l)
l) is 2.798 and the protein concentration (g / l) is 0.933, which is a high value, indicating that kitchen garbage can be solubilized at a high rate. In addition, it can be seen that the solubilization rate does not decrease even when the concentration of carbonate ions becomes higher.

(2) Example 2 Kitchen garbage also in the presence of water was subjected to various treatment temperatures by changing the treatment temperature to 10 wt%, a carbonate ion concentration of 1000 ppm, and a treatment time of 1 hour as shown in Table 3. Solubilized. The results were as shown in Table 4.

[Table 3] [Table 4] As is clear from Table 4, when the treatment temperature is 120 ° C. or higher, organic substances can be decomposed at a high rate of 75% or more as shown in Category 2. At this time, the sugar concentration (g / g / l) is 1.211, COD concentration (g / l) is 2.57
3. Since the protein concentration (g / l) was 0.629, which was a high value, it was found that kitchen garbage could be solubilized at a high rate. When the treatment temperature is increased, the organic matter decomposition rate increases. However, when the temperature reaches 350 ° C., which is close to the critical temperature of water, the sugar concentration (g / l), the COD concentration (g / l), and the protein concentration ( g / l) decreases.

[0032]

As described above, according to the method for solubilizing organic waste of the present invention, the concentration of carbonate ion is 1000 pp.
m or more and an aqueous solution obtained by dispersing the organic waste is heated at 120 to 350 ° C. in a closed vessel so that the organic waste is solubilized. Since the organic waste can be solubilized at a low temperature of about 120 ° C. without requiring such high-temperature, high-pressure treatment, the solubilization treatment can be performed at low cost, and the organic waste can be reduced by the presence of carbonate ions. It can be solubilized to a high level and has a carbonate ion concentration of 1
In the case of an aqueous solution material in which less than 000 ppm of organic waste is dispersed, Na, K, Ca, M
g, a carbonate or bicarbonate having Ba or NH ₄ as a cation, or a mixture thereof is added, and the mixture is placed in a closed container at 12
By performing the heat treatment at 0 to 350 ° C., the organic waste can be similarly solubilized, and even if an excessive amount of carbonate or the like is added, the solubilization performance does not decrease.
The operability is extremely easy. Further, instead of directly adding a carbonate or the like to the aqueous solution raw material,
By aerating a gas containing carbon dioxide and heat-treating it at 120 to 350 ° C. in a closed container, the organic waste can be solubilized in the same manner as described above, and the boiler exhaust gas and digester exhaust gas can be used as the gas. Can be used and can be implemented at a low cost with simple equipment.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of a method for pretreatment of organic waste digestion of the present invention.

FIG. 2 is a schematic diagram showing another embodiment of the present invention.

FIG. 3 is a schematic diagram showing still another embodiment of the present invention.

FIG. 4 is a schematic diagram showing still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic waste 2 Water 3 Slurry (aqueous solution raw material) 4 Solubilization tank (closed vessel) 9 Additive 10 Gas 11 Digestion residue (aqueous solution raw material)

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Ryuzo Hiraoka 1 Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term in the Technical Research Institute, Kawashima-Harima Heavy Industries Co., Ltd. 4D004 AA01 AA02 AA03 AA04 AA12 CA18 CA22 CA34 CA50 CC01 CC03 CC11 DA01 DA02 DA03 DA06 DA10 4D059 AA01 AA05 AA07 AA08 BA12 BA21 BF02 BF15 BK16 DA01 DA02 DA37 DA38 DA41 EA20 EB06 EB20

Claims (3)

[Claims] 1. An aqueous raw material having a carbonate ion concentration of 1000 ppm or more and an organic waste dispersed therein is heated to 120 to 350 ° C. in a closed vessel,
A method for solubilizing organic waste, comprising solubilizing the organic waste. 2. An aqueous solution raw material having a carbonate ion concentration of less than 1000 ppm and an organic waste dispersed therein contains N
a, K, Ca, Mg, Ba or a carbonate or bicarbonate having NH ₄ as a cation, or a mixture thereof,
A method for solubilizing organic waste, wherein the organic waste is solubilized by heat treatment at 120 to 350 ° C. in a closed container. 3. A gas containing carbon dioxide gas is aerated in an aqueous solution material having a concentration of carbonate ions of less than 1000 ppm and an organic waste dispersed therein, and a gas containing 120 to 3 carbon dioxide is contained in a closed container.
A method for solubilizing organic waste, wherein the organic waste is solubilized by heat treatment at 50 ° C.